This invention relates to a ground engaging device for raising the rear end of a truck trailer during docking, and more particularly to a lifting device which is movable from a flat position on the ground to an inclined position. The device operates to elevate the bed of a trailer to the level of a dock to facilitate loading and unloading of cargo.
In order to load and unload a trailer, it is normally backed up against a raised dock. In many cases, the bed of the trailer is considerably lower than the level of the dock. In some cases, it is possible to use a platform extending from the dock to the bed of the truck, provided that the angle of inclination is not too severe. If the bed of the truck is especially low, however, a separate lift is employed beneath the rear wheels of the truck.
Present day truck lifts are designed to be level with the ground and comprise a hydraulically operated platform. The rear wheels of the trailer are backed onto the platform, and the platform is then inclined upwardly to lift the rear end of the trailer.
All prior and current lifts of the foregoing nature require a pit to be excavated beneath the lift and lined with concrete. The use of a pit has been considered essential for several reasons. First, the power cylinders and other operative components are contained in the pit. Second, the construction of the platform requires substantial reinforcement to support the heavy weights being lifted, i.e., up to 50,000 pounds. The reinforcing beams for the platform occupy considerable thickness, which is accommodated by the pit when the lift is in a lowered position.
There are many serious drawbacks with truck lifts which require use of a pit. The cost of the excavation, concrete work, piping, etc., is very high and may contribute up to 50 percent of the cost of installation. Installation of a pit at an existing site may be extremely difficult or impossible. Moreover, the installation is considered to be permanent, in that the lift equipment cannot be moved or relocated without construction of a new pit.
All of the foregoing problems, together with the use of lower trailer beds, have created the need for a lift which is more adaptable than those currently available in the art.